Role of chromium in human metabolism, with special reference to type 2 diabetes.

It is recognised as a nutritionally essential element with daily adequate intake (AI) of 25 μg for women and 35 μg for men and with serum levels in healthy humans from developed countries of 2.3 40.3 nmol/l. The US Environmental Protection Agency (EPA) has replaced acceptable daily intake with calculated reference dose (RfD). The RfD is calculated from the ‘no observed adverse effect level’ from animal or human experiments and applying a “uncertainty and modifying factor” to it. The reflects a staggering 350 times the ‘estimated safe and adequate dietary intake’ of 50-200 μg. The ratio of RfD to estimated safe intake is less than two for zinc, about two for manganese and about six for selenium. The ‘estimated safe and adequate dietary intake’ being 350 times less than the RfD reflects the lack of toxicity or adverse effects of chromium III, and probably dietary supplementation is greatly underdosed.